The Mechanisms and Regulation of Placental Amino Acid Transport to the Human Foetus

Cleal, Jane K.; Lewis, Rohan M.

doi:10.1111/j.1365-2826.2008.01662.x

Cited by 129 publications

(119 citation statements)

References 82 publications

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“…Regarding amino acids and monoamines, 17 mammalian transport systems for amino acids have been functionally identified in the human placenta [119,120] . The interaction of xenobiotics with amino acid transport systems in the syncytiotrophoblast may result in a deficit in the transport of amino acids across the placenta.…”

Section: Protection Against Drugs and Toxinsmentioning

confidence: 99%

Excretion of biliary compounds during intrauterine life

Macı́as¹,

Marin²,

Serrano³

2009

WJG

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In adults, the hepatobiliary system, together with the kidney, constitute the main routes for the elimination of several endogenous and xenobiotic compounds into bile and urine, respectively. However, during intrauterine life the biliary route of excretion for cholephilic compounds, such as bile acids and biliary pigments, is very poor. Although very early in pregnancy the fetal liver produces bile acids, bilirubin and biliverdin, these compounds cannot be efficiently eliminated by the fetal hepatobiliary system, owing to the immaturity of the excretory machinery in the fetal liver. Therefore, the potentially harmful accumulation of cholephilic compounds in the fetus is prevented by their elimination across the placenta. Owing to the presence of detoxifying enzymes and specific transport systems at different locations of the placental barrier, such as the endothelial cells of chorionic vessels and trophoblast cells, this organ plays an important role in the hepatobiliary-like function during intrauterine life. The relevance of this excretory function in normal fetal physiology is evident in situations where high concentrations of biliary compounds are accumulated in the mother. This may result in oxidative stress and apoptosis, mainly in the placenta and fetal liver, which might affect normal fetal development and challenge the fate of the pregnancy. The present article reviews current knowledge of the mechanisms underlying the hepatobiliary function of the fetal-placental unit and the repercussions of several pathological conditions on this tandem.

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Section: Protection Against Drugs and Toxinsmentioning

confidence: 99%

Excretion of biliary compounds during intrauterine life

Macı́as¹,

Marin²,

Serrano³

2009

WJG

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“…This type of growth pattern is usually associated with decreased cell size or mass and foetal weight with less effect on total cell number and other foetal body measurements (Gluckman & Hansan, 2004). In the present study, the disorder may be caused by selective effect of limited foetal metabolic substrate availability, resulting from decreased utero-placental exchange or perfusion associated with decrease placental weight (Thorens & Mueckler, 2010) or altered gene expression (Angiolini et al, 2006;Vallet & Freking 2007;Cleal & Lewis, 2008) imposed by dexamethasone. The mechanism seems to have some elements of interspecies variation as the Yankasa sheep were more prone than those of goats.…”

Section: Discussionmentioning

confidence: 73%

Comparative effects of dexamethasone on placental and foetal organ weights and some linear body measurements in Yankasa sheep and Sahel goats

Yahi¹,

Ojo²,

Mshelia³

et al. 2017

Sokoto J. Vet. Sc.

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Dexamethasone is a potent synthetic glucocorticoid use in veterinary and human medicine. However, it causes intra uterine growth restriction (IUGR) and decreases birth weights in some animal species and humans, although each species respond differently. This study investigated the effects of dexamethasone on placental weights and some foetal parameters in Yankasa sheep and Sahel goats with known average gestational length of 148.35 ± 1.50 days and 148.33 ± 1.58 days respectively. Ten adult Sahel goats comprising 8 does and 2 bucks and 10 Yankasa Sheep comprising of 8 ewes and 2 rams were used for this study. Pregnancies were achieved by natural mating after synchronization. Repeated dexamethasone injections were intramuscularly given at 0.25mg/kg body weight on days 1, 3 and 5 during first trimester and days 51, 53 and 55 during second trimester. Foetuses were harvested at day 78 of gestation all through Caesarean section. Foetal weights, crown-rump lengths (CRL), height at withers, heart girth, abdominal circumference, weights of adrenal glands and placental weight were evaluated. Specimens from placentas and adrenal glands were collected for histological analysis. Results showed that the mean placental weights, placental efficiency and foetal body weights were significantly (P<0.05) decreased in dexamethasone treated sheep and goats compared to controls. There was no significant change in foetal adrenal glands and linear body measurements between dexamethasone treatment and control groups in both species except crown-rump lengths (CRL) which was significantly (P<0.05) reduced in Sheep foetuses. It was concluded that dexamethasone caused significant decrease in placental weights and placenta efficiency and hence placental-maternal-foetal transport of nutrient materials in both species and also caused decrease in foetal crown-rump-lengths in sheep but not in goats. This suggests that dexamethasone has some teratogenic effects and that Sheep are more susceptible to dexamethasone treatment compared to goats.

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“…Amino acids are transferred across the placenta by active transport using a complex system with more than 10 different families of amino acid carriers: systems A, L, yþ, yþL, T, X -AG and ASC (Table 1) [36,37]. These carriers can be classified in two classes: accumulative amino acid transporters (mainly represented by system A and X -AG ) and amino acid exchangers (LAT1, LAT2, yþLAT1, yþLAT2 and ASC) [37].…”

Section: Mechanisms Involved In the Placental Amino Acid Transfermentioning

confidence: 99%